1. Field of the Invention
The invention presented herein relates to circuitry for the validation of repetitive signals such as those initiated by an optical energy emitter mounted on a vehicle wherein the circuitry is useful in a traffic signal control system which can be remotely changed from a normal traffic mode of operation to an optical energy emitter mode of operation and, more particularly, to the use of a microprocessor as a part of such circuitry.
2. Description of the Prior Art
U.S. Pat. No. Re. 28,100 discloses a traffic signal remote control system in which a pulsed beam of high intensity light transmitted at a predetermined frequency from an emergency vehicle is detected at a controlled traffic intersection and is used to initiate the operation of circuitry operatively connected to the traffic light signal controller for the intersection so a green light will be provided for the emergency vehicle. Such pulses of light are distinguished from the steady state ambient light by the use of a detector which responds only to light pulses which increase in intensity at a very fast rate. The possibility of the system responding to false signals is reduced further by integrating the signals received so a number of the pulses must be received within a short time to provide a signal of sufficient magnitude to cause the remote control system to provide the desired control of the traffic light signal controller.
It was found that the signal discrimination provided by the system described in the above-mentioned patent does not adequately discriminate between a series of equally spaced light pulses and a series of irregularly spaced light pulses. U.S. Pat. No. 4,230,992 discloses a signal discriminating circuit that provides the needed discrimination, but requires the use of a number of discrete, dedicated circuits.